The objective of this proposed research is to develop a new fiber sensor technology based on detection of SP oscillations with the specific goal of designing a simple, low-cost, remote optical probe capable of measuring HIV and other viral antibodies upon direct contact with a suitable biological fluid.The sensor will be capable of detecting a specific immunological reaction between proteins immobilized onto the fiber sensor and their corresponding binding partners in solution, without the requirements of molecular tagging employed in conventional immunoassay procedures. Therefore, the proposed technology will be important for in vitro, ex vivo, and in vivo diagnosis of infectious agents. In Phase I study, the investigators will carry out research to understand and control the SP oscillations in optical fibers. The feasibility for immunosensing applications will be tested by use of a model system composed of human chorionic gonadotropin (HCG) molecules immobilized on the sensor tip for specific determination of low concentrations of anti-HCG in solution. Phase II research will use the technology developed in Phase I study to build a prototype device sensitive enough to measuring viral antibodies in saliva. The analyte menu will include HIV, hepatitis, leukemia, and other viral antibodies of interest in the diagnostics of infectious diseases.